Hammer board for drop forge hammer



Nov. 17, 1964 c. H. VAN HARTESVELDT ETAL 3, 7,

HAMMER BOARD FOR DROP FORGE HAMMER Filed Feb. 29, 1960 (arrall H lzn l/arlesVc/di Buddy 0. Wait United States Patent 3,157,069 HAMMER EGARD FGR DROP FORGE HAMMER Cmroll H. Van Hartesveldt and Buddy D. Wahl, Toledo, Ohio, assignors, by mesne assignments, to Hoover Ball and Hearing Company Filed Feb. 29, 1960, Ser. No. 11,763 6 Claims. (Cl. 78-25) The present invention relates to an improved drop forge machine and particularly to a drop forge hamme board.

The present invention contemplates the provision of an improved board of the type which is secured to a drop forge hammer and utilized for repeatedly raising the hammer so that it can be dropped on a workpiece. Drop forge machines utilizing hammer boards provide counterrotating friction rolls which are mounted so as to be laterally shiftable to frictionally engage the board and raise it to lift the hammer. The friction rolls are then moved apart to release the board and drop the hammer on a workpiece. Friction rolls are normally adjustable and permit wear on hammer boards to a maximum depth of .090" after which the hammer boards are re-cut so that a different surface area will be engaged by the friction rolls.

An object of the invention is to provide an improved hammer board in combination with a drop forge hammer machine which substantially increases the period of continuous operation possible before requiring resetting of the machine due to hammer board wear and before requiring re-cutting of the hammer board.

Another object of the invention is to provide an improved ham-mer board for a drop forge machine of the type described which has a greatly increased operating life but is relatively simple and inexpensive to manufacture and presents substantially no disadvantages in comparison with hammer boards of the type now in use.

Other objects and advantages will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings, in which:

FIGURE 1 is :an elevational view shown in schematic form of a drop forge machine in accordance with a preferred form of the present invention;

FIGURE 2 is a vertical sectional view taken substantially along line II-II of FIGURE 1;

FIGURE 3 is a vertical sectional view illustrating steps in the manufacture of a hammer board in accordance with the present invention; and

FIGURE 4 is a vertical sectional view taken through a hammer board having a preferred structure.

As shown on the drawings:

As illustrated in FIGURE 1, the drop forge machine which is shown somewhat schematically with parts omitted for clarity employs a pair of counter-rotating friction rolls 5 and 6 rotating in opposite directions as indicated by the arrows on the rolls. Extending substantially vertically between the rolls is a hammer board 7. The hammer board will be snatched and drawn upwardly by bringing the rolls together against the outer flat surfaces of the board. The board will be released by moving the rolls 5 and 6 laterally apart, thus giving movement to the board as indicated by the arrowed line above the board. The lateral movement of the friction roll-s is indicated by the arrowed lines directly beneath the rolls.

The rolls rotate on axes 8 and 9 and are supported on arms 10 and 1-1. These arms are suitably pivo-tally supported at 12 and 13 so as to move the rolls 5 and 6 laterally together or apart with pivotal movement of the arms.

As will be recognized, more refined supports for is preferably compressed to a thickness of .090.

A 3,157,069 Patented Nov. 17, 1964 the friction rolls 5 and 6 may be employed, with the present schematic showing chosen for clarity.

Secured at the lower end of the board is a drop forge hammer 14. Below the hammer is a support 15 for a workpiece 16 which is shaped :by repeated dropping of the hammer 1'4 thereon. The hammer board 7 is detachably secured to the hammer 14 by suitable means illustrated at 14a so that the hammer board may be disconnected from the hammer 14 and re-cut to bring a different surface area opposite the friction rolls 5 and 6 after wear occurs in one location in the hammer board. As illustrated in FIGURE 2, the hammer board 7 may be comprised of a plurality of individual strips which are not attached but are in side-by-side relationship. The strips are shown at 7a, 7b, 7c and 7d. The wood is preferably vertically grained maple with the surface layer compressed, as will be described, perpendicular to the grain and approximately parallel to the plates of summer wood.

For pivoting the arms :10 and 11 vertical rods 17 and 18 are reciprocated vertically in the direction of the arrows below the rods by suitable operating mechanism. The closed position of the friction rolls 5 and 6, and the distance between them, is limited by adjustable stop mean-s illustrated in the form of stop members 19 and 20 secured to the rods 17 and 18 and positioned to engage adjustable stops 21 and 2.2. Friction rolls such as 5 and 6 on drop forge machines are normally adjustable to allow wear on hammer boards to a maximum depth of .090", after which the boards are re-cut.

The hammer board of our invention has a hardened compressed outer surface to be engaged by the friction rolls which greatly resist the wear incurred by the rolls being brought together to engage and snatch the board upwardly after the hammer has been dropped. By increasing the wearing life of the outer surface of the board the frequency of readjustment of the closed positions of the friction rolls is decreased and the frequency of re-cutting the boards is greatly decreased, .therefore increasing production rate and reducing the consumption of hammer boards by the drop forge machine.

The hardened outer surface of the hammer board 7 is obtained by compressing an outer layer of the wood to beyond its elastic limit to obtain a permanent increase in wood density. In a preferred form, as illustrated in FIGURE 4, the outer surfaces of the boards are compressed to form outer layers 22 and 23 which present hardened outer surfaces 22a and 23a to the friction rolls. The hardened layers are backed by a core 24 of wood of normal density, which is preferably integral with, and of one piece with the hardened outer layers 22 and 23.

In a further preferred form, the hardened outer layers 22 and 23 have an outer surface 22a and 23a compressed substantially to maximum density of the wood which has a specific gravity of 1.3 to 1.4. The outer layer The wood below the outer surface decreases substantially linearly in density for the thickness of the layers 22 and 23 to the core. 24. The core 24 is of the natural density of the wood thereby providing a support of relatively light weight and being relatively resilient. For example,

if maple is used, which has a natural density of .7, the core will have a natural density of .7. We have found maple toprovide substantial advantages over other types of wood used in affording optimum performance and long wearing life apparently not directly related to such physical characteristics of the wood as specific gravity, as compared with other wood, although in certain circumstances other types of Wood may be employed in accordance with the principles of the present invention. Maple is a preferred form of wood, at least for the outer hardened layers.

Hammer boards constructed in accordance with the above features and formed of maple with the outer layer fully compressed at the surface and diminishing substantially linearly in density provide an increased amount of wood available up to 100% over wood of natural density. While it could be expected that the life of such a hammer board would be increased up to 100% we have found that the life has been increased by 2 /2 to 4 times. For example, an ordinary maple board operating under substantially the same environment and in the same machine provided an operating life for forging from 4,500 to 6,000 parts before requiring resetting the board. A board formed with a case hardened surface in accordance with the present invention permitted forging of 16,850 parts without necessitating relocating the wear point.

The hardened surface layers 22 and 23 may be stabilized to prevent their being adversely affected by moisture. Stabilization may be accomplished by heating from 300 to 360 F. while holding the wood compressed during formation of the hardened surface layers. Stabilization may also be accomplished to prevent entry of moisture or to prevent the escape of moisture by impregnating the hardened surface with a sealant such as phenolic resin to provide a moisture barrier and a tough surface which will not wear away quickly.

FIGURE 3 illustrates steps of a method for forming the hardened layers on the surface of the hammer board. Basically, the method embodies applying a pressure to the surface of the wood over a limited area to exceed the elastic limit of the wood. The application of pressure to the limited area is progressively shifted along the wood to enlarge the compressed area until the entire surface layer is permanently compressed.

As illustrated in FIGURE 3, the hammer board 7 is prepared by drawing through shoe or mandrel assemblies 25 and 26. The different strips 7a, 7b, 7c and 7d of the hammer board may be prepared together or separately.

The board is first treated with a phenolic resin in a tank 26a to impregnate the surface. This may be accomplished by dipping or other suitable means and impregnation may be aided by overnight heating in an oven, not shown. The board is moved from the tank in the direction of the arrow 27 whereupon it passes between banks of lamps 28 and 28a which heat the surface of the wood to a temperature to remove the surface moisture which may have accumulated, and to B-stage the phenolic resin. Other forms of sealant may be used in some circumstances such as wax or thermosetting plastic. The preheat lamps 28 and 28a heat the wood from 250F. to 360 F. The preheat lamps substantially heat only the surface of the wood and do not heat it to the depth of compression inasmuch as excessive heating will unduly soften the wood fibers.

Preheating of the wood surface to the compression depth may be performed by preheating blocks 33 and 34 which have flat surfaces riding on flexible shims or sheets 29 and 30 positioned over the surfaces of the wood. These shims may be of brass or flexible steel preferably such as 1095 steel and will be anchored at the lead end of the wood so as to be drawn along therewith. A lubricant such as graphite or mineral oil is employed between the shims and the mandrel assemblies 25 and 26. The preheat blocks 33 and 34 impart sufficient heat to the wood to bring it to a temperature above 212 F. to soften the surface fibers of the wood.

The surface layers of the wood are compressed by inclined shoe or mandrel surfaces 31 and 32 which compress the wood surface in excess of its elastic limit. The slope of the inclined surfaces 31 and 32 has critical limits and must have a sufiicient incline to overcome the compressive strength of the surface layer of the wood and yet must not be excessively sharp so as to shear off the layer of the wood. We have discovered that a slope having a ratio of horizontal length to vertical height of 2:1 is optimum, but the slope should not be greater than a ratio of 1:1 and should not be flatter than a ratio of 6:1

for practical usage. After the wood has been compressed by the sloping surfaces 31 and 32 it is stabilized by post heating to a temperature of 300 F. to 360 F. by the blocks 36 and 37. To prevent the moisture in the wood from flashing to steam to dry the surface and to prevent the causing of blisters the surface is then cooled to a temperature below 210 F. by cooling blocks 38 and 39, insulated from the blocks 36 and 37 by insulating walls 40 and 41.

It Will of course be understood that the various stages of the mechanism of FIGURE 3 may be omitted and that basically the compression by the inclined surfaces 31 and 32 is all that is required. The application of preheat by the blocks 33 and 34 facilitates ease of compression and the application of post heat by blocks 36 and 37 stabilizes the compression while cooling prevents drying of the surface. The application of a sealant also stabilizes the surface and prevents the escape of moisture. It will also be understood that other means may be employed for compressing the surfaces of the board such as rollers which apply a force to a limited area to overcome the compressive strength of the wood and have critical relationships of the length of step of wood engaged to the ieight of compression within the limits of 6:1 and 1:1 as above described.

The wood may be preheated before putting it through the mandrel to reduce the forces necessary. When this is done the mandrel design must be calculated using the Wood properties at the temperature chosen.

When wood is physically compressed as described above, it takes a permanent set. However, if it is wet subsequently, it tends to return to its former state. By heating to 300360 it can be stabilized. In our process the compressed layer is stabilized by heating the mandrel and pushing the wood through slowly enough to first cornpress and then stabilize the wood. Also, heating the wood by a portion of the mandrel prior to its passing by the compression step plasticizes the surface sufiiciently to resist fiber fracture.

In order to apply a durable and waterproof surface to the compressed and stabilized case, we have found it desirable to soak the boards prior to processing in a 20% water solution of unpolymerized phenolic resin components. Then with the mandrel at 350 F. we not only case harden the wood by compressing and stabilizing it, but we also create a cured phenolic resin surface. Because the phenolic solution does not penetrate far and because this surface material is compressed to about onehalf its original thickness, the layer is only a few thousandths of an inch thick.

A most important feature of the use of phenolic resin components described above is the sealing of the wood surface during the case hardening process. Without it, we have found that the compressed surface becomes extremely dry as indicated by its lateral shrinkage even though it would be expected to bulge the top surface of the board at its unsupported sides. Our best result is attained by using a radiant heater above the surface of the wood at its entrance to the mandrel. The intensity of heat is set to bring the surface of the wood to 300 F. for 20 seconds. This dries the phenolic resin solution and takes it to a B-stage. This seals the wood surface before its subsequent travel under the mandrel.

In calculating the slope and height of a compression step there are several practical limitations to be considered. If the step is too steep, shearing forces set up would strip off the top layer of wood. An incipient condition of this nature would break up the wood fibers being compressed at the surface by bending them too sharply. Likewise, too steep and short a compression step would work the traveling shim past its elastic limit. These limitations can be alleviated somewhat by faring the lead-in and exit contours of the step.

As the slope of the shoe is made flatter, the case hardening effect becomes less and less until the density gradient becomes so gradual that nothing significant is accomplished.

As used hereinbefore in the specific examples, the terms resin and B-stage resin makes specific reference to 20% aqueous phenol-formaldehyde resins. These resins may be converted to the B-stage by preliminary heating and ultimately thermoset during the passage between the mandrels. Resins of this type are particularly suitable in the practice of the invention. On the other hand, it will be appreciated that satisfactory results may also be obtained using numerous other phenolic resins, such as the alkyl phenol-formaldehyde resins (e.g. p-tert. butylphenol-formaldehyde resins). In addition, other resinous aldehyde condensation products may be used to impregnate the wood surface. Such other aldehyde condensation products include the well-known urea-formaldehyde, melamine-formaldehyde, benzoguamineformaldehyde (and other triazine-forrnaldehyde resins wherein the triazine has at least two unsubstituted amino groups), toluenesulfonamide-forrnaldehyde resins, etc. Preferably the resins of this class that are used are thermosetting resins which in their early stages of condensations are water-soluble so that they may be more readily applied to the wood and cause to impregnate the same. Moisture barriers may, however, be provided for the purpose of the instant invention by various thermoplastic resins which may be caused to impregnate the wood to at least a limited extent. In using such resins the wood material is adequately cooled before it is released from the mandrels.

The resins are usually used in conjunction with a polymerization catalyst and/ or accelerator; but such compositions are conventional and need not be described in greater detail herein.

Another type of resin which has been found to be suitable is a polymerizable unsaturated polyhydric alcohol-polycarboxylic acid polyester, which is prepared by reaction of one or more polyhydric alcohols and one or more polybasic acids. Such a resinous material is used to impregnate the wood surface in substantially the manner hereinbefore described in connection with phenolic resins. The proportion of polyhydric alcohols having more than two hydroxy groups, such as glycerol or pentaerythritol, and the proportion of polycarboxylic acids having more than two carboxylic acids having more than two carboxy groups, such as citric acid, preferably is small so that in the production of the polyester there may be maximum esterification of the hydroxy and carboxy groups without attainment of excessive viscosity. Ordinarily it is desirable that the unsaturated polyester be polymerizable into an infusible or high melting point resin, so that the proportion of unsaturated components should be such that the polyester contains an average of more than one double bond per molecule; for example, there may be an average of eleven or more double bonds in every ten molecules of the polyester.

The present invention is applicable to all polymerizable unsaturated polyhydric alcohol-polycarboxylic acid polyesters. A typical example of such a polyester is a prod uct prepared by the reaction of an unsaturated dicarboxylic acid such as maleic, fumaric, itaconic, citraconic or mesaconic acid with a dihydric alcohol such as any polymethylene glycol in the series from ethylene glycol to dccamethylene glycol, propylene glycol, any butylene glycol, any polyethylene glycol in the series from diethylene glycol to nonaethylene glycol, dipropylene glycol, any glycerol monobasie acid monoester (in either the alpha or beta position), such as monoforrnin or monoacetin, any monoether or glycerol with a monohydric alcohol, such as monomethylin or monoethylene, or any dihydroxy alkane in which the hydroxy radicals are attached to carbon atoms that are primary or secondary or both, in the series from dihydroxy butane to dihydroxy decane.

Part of the unsaturated dicarboxylic acid may be replaced by a saturated dicarboxylic acid, such as any normal acid in the series from oxalic acid and malonic acid to sebacic acid, or any benzene dicarboxylic, naphthalene, dicarboxylic or cyclohexane dicarboxylic acid, or diglycolic, dilactic or resorcinol diacetic acid. All of the unsaturated acid may be replaced by a saturated acid if a polyhydric alcohol is present whose molecule has two or three free hydroxy groups and consists of an ether of one or two molecules of allyl or methallyl alcohol with one molecule of a polyhydroxy compound such as glycerol, pentaglycerol, pentaerythritol butantetrol-1,2,3,4, a trihydroxy normal alkane having from four to five carbon atoms such as butantriol-l,2,3, or a monoalkyl ether of pentaerythritol or butantetrol-1,2,3,4 in which the alkyl radical has from one to four carbon atoms and has from one to two hydrogen atoms attached to the same carbon atom as the ether linkage, such as the monomethyl or monoisobutyl ether of pentaerythritol.

In the preparation of the polymerizable unsaturated polyester, any of the usual modifiers such as monobasic acids, monohydric alcohols and natural resin acids may be added. The larger the proportions of monobasic acids and monohydric acohols, the lower is the average number of acid and alcohol residues in the resulting polyester molecules, and the lower is the viscosity of the polyester. On the other hand, the more nearly equal the molecular proportions of dibasic acid and dihydric alcohol, the greater is the average number of residues in the resulting polyester molecules, and the greater is the viscosity. The proportions of ingredients used are those proportions that produce a polymerizable polyester of the desired viscosity. Other properties of the polyester, such as solubility in various solvents, also may be varied by selecting various reacting ingredients and varying their proportions. The infusibility, hardness and inertness of the product obtained by polymerization of the polyester may be increased by varying the initial reacting ingredients to increase the average number of double bonds per molecule of the polymerizable polyester.

The point to which the reaction of the ingredients is carried in the preparation of the polymerizable polyester is simply that point at which the product has the desired consistency. The consistency or viscosity of the polyester varies directly with the average number of acid and alcohol residues in the molecule. For example, the average number of residues in the molecule of the polyester may vary from about three to about one hundred twenty.

The reaction is carried out at a temperature high enough and for a time long enough to secure the desired consistency. An elevated temperature preferably is employed to expedite the reaction, but during the preparation of the polyester, the temperature should not be so high nor the time of reaction so long as to cause sub stantial polymerization. There is less danger of premature polymerization if an inhibiting agent is added before the esterification is carried out.

The preparation of the unsaturated polyester preferably is carried out in an atmosphere of an inert gas such as carbon dioxide, nitrogen or the like, in order to prevent darkening or to make it possible to obtain a pale or colorless product. Bubbling the inert gas through the reacting ingredients is advantageous in that the gas serves the added functions of agitation and of expediting the removal of water formed by the reaction. It is desirable to exclude oxygen, which causes discoloration.

Polymerization of these materials usually is carried out at temperatures of about to about F. A solution comprising one or more polymerizable unsaturated polyesters and one or more polymerizable monomeric allyl esters hereinbefore described is particularly useful. Either the unsaturated polyester or the allyl ester or both may be partially polymerized before the ingredients are mixed. Allyl esters that are useful for the preparation of such a solution include diallyl phthalate, diallyl oxalate,

diallyl diglycolate, triallyl citrate, carbonyl bis-(allyl lactate) maleyl bis-(allyl lactate), fumaryl bis-(allyl lactate), succinyl bis-(allyl lactate), adipyl bis-(allyl lactate), sebacyl bis-(allyl lactate), phthalyl bis-(allyl lactate), fumaryl bis-(allyl glycolate), carbonyl bis-(allyl glycolate), carbonyl bis-(allyl salicylate), tetra-(allyl glycolate) silicate, and tetra-(allyl lactate) silicate. Such a solution, which usually contains about 20 to 80 percent of the allyl ester and about 70 to 80 percent of the polymerizable polyester, is particularly advantageous because the polyester has desirable physical properties and hardens very rapidly after the initial polymerization whereas the presence of the allyl ester causes the polymerized product to be much more water resistant and insoluble. Moreover, the combination of the polyester and the allyl ester usually polymerizes more rapidly than either of such substances alone. (The terms parts and percent, as used herein to refer to quantities of material, means parts and percent by weight.)

A similar solution may be prepared by dissolving the polyester, before use, in a polymerizable substance such as styrene, vinyl acetate, methyl methacrylate or methyl acrylate.

Thus it will be seen that we have provided an improved drop forge machine with an improved hammer board for reliable operation which meets the objectives and advantages hereinbefore set forth. The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited to the specific forms disclosed, but covers all modifications, changes and alterna tive constructions and methods falling within the scope of the principles taught by the invention.

We claim as our invention:

1. In combination in a drop forge hammer, a pair of counter-rotating hammer raising friction rolls, means for shifting the position of said friction rolls to raise or lower a forge hammer, a hammer board extending vertically between said friction rolls and being of wood with hardened outer layers facing the friction rolls having a specific gravity of 1.3 to 1.4 with the density of the outer layers decreasing inwardly substantially linearly to wood of its original density, a drop hammer secured to the lower end of the board, and a work support beneath said hammer.

2. In combination in a drop forge machine, a pair of counter-rotating hammer raising friction rolls, a wood hammer board extending vertically between said friction rolls and having hardened outer surfaces facing the friction rolls formed by compressing only the outer surfaces of the wood beyond their elastic limit with the compressed wood being stabilized by heating while compressed, means for laterally shifting the position of the friction rolls to engage or disengage the board surfaces and raise or lower a forge hammer, a drop hammer secured to the lower end of the board, and a work support beneath the hammer.

3. In combination in a drop forge machine, a pair of counter-rotating hammer raising friction rolls, a wood hammer board extending substantially vertically between said friction rolls and having hardened outer surface layers of wood compressed beyond their elastic limit with the inner core of the board being of substantially normal wood density, said board being formed of a single piece of wood for its depth between rolls, means for laterally shifting the position of said friction rolls to engage or disengage the board and raise or lower a forge hammer, a drop hammer secured to the lower end of the board, and a work support beneath the hammer.

4. A drop forge hammer board for securing to a drop hammer and extending between laterally shiftable counterrotating friction rolls for raising and dropping the hammer comprising an elongated board of substantially uniform thickness being of an integral single piece of wood through its thickness and having outer hardened surfaces with the wood compressed beyond its elastic limit and stabilized and having the wood betwen said surfaces of normal density.

5. A hammer board for a drop forge hammer having a pair of counter-rotating hammer raising friction rolls comprising a plurality of parallel strips of wood of uniform thickness for attachment to a drop hammer and extending between the rolls with the strips of Wood each having hardened compressed outer surface layers of wood supported by an inner core of wood of substantially natural density with the surface layers and core formed of one piece of wood for each strip.

6. In combination in a drop forge machine, a pair of counter-rotating hammer raising friction rolls, means for laterally shifting the position of said friction rolls to raise or lower a forge hammer, a unitary integral wood hammer board extending vertically between said friction rolls and having a depth of the wood extending inwardly a short distance from each of the outer surfaces compressed beyond its elastic limit with the wood of the board inwardly of said depth being of substantially normal density, a drop forge hammer secured to the lower end of the board, and a work support beneath said hammer.

References Cited in the file of this patent UNITED STATES PATENTS 1,455,420 Allen May 15, 1923 1,670,493 Clark May 22, 1928 1,709,599 Smith Apr. 16, 1929 1,812,464 Billings June 30, 1931 1,814,193 Smith July 14, 1931 1,899,371 Waldron Feb. 28, 1933 2,136,730 Sweetland Nov. 15, 1938 2,158,834 Robinson May 16, 1939 2,350,729 Crovet June 6, 1944 

1. IN COMBINATION IN A DROP FORGE HAMMER, A PAIR OF COUNTER-ROTATING HAMMER RAISING FRICTION ROLLS, MEANS FOR SHIFTING THE POSITION OF SAID FRICTION ROLLS TO RAISE OR LOWER A FORGE HAMMER, A HAMMER BOARD EXTENDING VERTICALLY BETWEEN SAID FRICTION ROLLS AND BEING OF WOOD WITH HARDENED OUTER LAYERS FACING THE FRICTION ROLLS HAVING A SPECIFIC GRAVITY OF 1.3 TO 1.4 WITH THE DENSITY OF THE OUTER LAYERS DECREASING INWARDLY SUBSTANTIALLY LINEARLY TO WOOD OF ITS ORIGINAL DENSITY, A DROP HAMMER SECURED TO THE LOWER END OF THE BOARD, AND A WORK SUPPORT BENEATH SAID HAMMER. 